Four years after a massive tower crane broke apart on E. 91st Street, crushing two workers under tens of tons of plummeting steel, a manslaughter verdict now looms for accused killer construction magnate James Lomma.

Manhattan Supreme Court Justice Daniel Convisor announced today that he will render judgement at 11:30 on Thursday, April 27 against Lomma, 66, whose crane-rental companies remain a fixture at major construction sites around the city, including at Ground Zero.

The judge will not elaborate on his verdict, he told a standing-room courtroom audience, which had just sat through a scathing afternoon summation by assistant district attorney Deborah Hickey.

“This crane collapse was as foreseeable as it was deadly,” Hickey, in her summations, told the judge, who has presided over two months of testimony in the non-jury trial.

It was the millionaire construction mogul’s greed that caused the two workers’ deaths, she said in her summations.

Lomma flouted Department of Buildings regulations, OSHA codes and industry standards in sending out to China for a cheap, quick-fix replacement bearing — a huge ring of metal that had been welded together so shabbily, it cracked into two pieces just five weeks after being installed, she said.

Everything above the cracked bearing — including the crane’s cab and its massive boom — fell 140 feet to earth. Crane operator Donald Leo, 30 — seen by eyewitnesses bracing himself within his cab, and looking skyward as it fell — was instantly crushed to death. Construction worker Ramadan Kurtaj, 27, his body battered on the ground by the fallen wreckage, died after five hours in the hospital.

Lomma had found the Chinese company on the Internet after more reputable US companies told him it would take at least a year to do the job — and every month the crane was out of commission it was costing Lomma $50,000 in rental fees, the prosecutor said.

He hired the company even after executives there initially expressed hesitancy over being competent to handle the complicated welding involved, according to testimony, writing Lomma, “Honest speaking, we don’t have confidence on this weld.”

Lomma further dropped the ball by leaving the job in the hands of his company’s $30-an-hour head mechanic, rather than hire an engineer to oversee the repair, the prosecutor told the judge. Lomma then left the doomed bearing inside the 91st St. crane after the Chinese company sent him a second bearing he’d also ordered, one that was so obviously cracked, “It looked like it would fall apart if you blew on it,” she told the judge.

The weld in the doomed 91st Street bearing, by virtue of its size alone, “had only a quarter of the strength it should have,” and its weakness was compounded by the company having rushed the critical cooling process, Hickey said.

Once installed, the bearing’s welded area continued to progressively deteriorate over its five-week lifespan, Hickey said, calling it, “Nothing more than a time bomb.”

“It was not a matter of whether it would fail. It was a question of when,” she said.

Defense lawyers Andrew Lankler and Paul Schechtman had argued in day-long closing statements yesterday that while the replacement bearing was indeed of inferior manufacture, and did crack in half, the real cause of the collapse was operator error.

Leo had reeled in the crane’s weighted hook so forcefully — an error called “two-blocking” — that it crashed into the boom tip assembly, causing the already over-extended, nearly upright boom to teeter, Lankler told Manhattan Supreme Court Judge Daniel Convisor, who is presiding over the non-jury trial.

That teetering and rocking was what strained the bearing to the cracking point, the lawyer said, pointing to weeks of defense engineering expert and eyewitness testimony. The bearing had passed several inspections and strength tests at that point, and would otherwise never have cracked, the lawyers argued.

“Mr. Lomma, New York Crane, were not aware of the risk that the crane would collapse,” Schechtman argued. “They have overcharged,” he said of prosecutors. “They have over-promised. They have over-sold.”

Hickey countered today that Lomma was basing these conclusions on the flawed testimony of high-price defense experts, one of whom had the audacity to take the stand and contend that the weld in the doomed bearing “is as good as you’re ever gonna get.”

“The next thing we were going to hear about were magical crop circles appearing in the weld,” the prosecutor snarked.

She called the defense contention that Leo had caused his own death by operator error “utterly unsupported by the laws of physics and engineering.”

Had Leo indeed two-blocked the crane, the impact of the hook and ball striking the boom tip “would have created an axial force, straight up and down,” that “would actually have helped the weld, by compressing it,” she argued. Blaming the victim “added insult to grievous injury,” she added.

Two of Lomma’s cranes collapsed in 2008, though he was only charged in the 91st Street incident. The manslaughter trial of a master crane rigger blamed in the second collapse, on E. 51st, which killed seven, ended in acquittal by bench trial in July, 2010.

Lomma faces a potential maximum of 15 years prison if convicted of the top manslaughter charge.